1. Field of the Invention
This invention relates to a method of raising sea-water fish, a display tank for sea-water fish and tank system for raising sea-water fish.
2. Description of the Prior Art
As personal interests have diversified in recent years, there are many homes which false pet animals indoors.
However, even within the range of personal interests, because animals are raised, some problems have arisen. For example, a certain amount of space is required for raising animals and noise caused by such animals may disturb other people in the neighborhood.
In view of this background, the number of homes in which display fish, such as tropical fish for example, are raised has been increasing recently, since they can be raised and appreciated in a limited space even in the home.
Display fish are highly valued as pets since they do not need a large space to be raised, produce no bad smells and make no noise.
For this reason, there are many homes in which display fish are raised. In this regard, most of such homes raise fresh-water fish. However, very few of such homes raise sea-water fish for display purposes.
In reality, sea-water fish are very colorful and very active due to their quick movements, and therefore it can be said that for display purposes they are even more suitable than fresh-water fish. However, raising sea-water fish for display purpose has not been popular so far.
This is because sea-water fish must be raised in an environment consisting of water which contains salt, and this can lead to a reduction in the amount of oxygen dissolved therein. As a result, bacteria which dislike oxygen are more likely to propagate.
When bacteria which dislike oxygen, namely anaerobic bacteria, are growing, the waste products etc. are inevitably converted into sulfides which are very toxic.
As a result, there arises problems in raising sea-water fish for display purposes. Namely, it becomes difficult to maintain a proper environment for raising sea-water fish.
In other words, in order to keep sea-water fish over a prolonged period of time, it is necessary to provide an environment in which the fish themselves can thrive easily. In this case, it can be said that an environment in which they can thrive easily is, in practice, an environment from which harmful or lethal agents or factors have been removed or eliminated as much as possible.
Factors which are lethal to sea-water fish can be listed as follows:
1. Abnormal specific gravity (salt concentration) (Outside the range 1.016-1.024) PA1 2. Abnormal water temperature PA1 3. Abnormal pH (Outside the range 7.5-8.2) PA1 4. Insufficient food PA1 5. Excessive numbers of fish PA1 6. Deterioration of water quality PA1 7. Oxygen deficiency PA1 8. Trouble between fish (preying on each other, disputes, cannibalism etc.) PA1 9. The outbreak of disease (Cryptocaryon irritans)
(a) Outside the range 20.degree.-30.degree. C. PA2 (b) Sudden changes in water temperature PA2 (a) A number of fish exceeding the limit for the number which can be tolerated in the tank. PA2 (b) Fish of a size exceeding the limit for the volume of fish which can be tolerated in the tank. PA2 (a) The admixture of impurities. PA2 (b) Ammonia formation. PA2 (c) Nitric acid formation. PA2 (d) The formation of poisonous gases by anaerobic bacteria. PA2 (a) White spot disease PA2 (b) Lymphocystis PA2 (c) Trichodina PA2 (d) Finrot PA2 (e) Pop-eye PA2 (f) Oodinium PA2 (g) Nutritional disease (Desease for refusing foof) PA2 (h) Parasites PA2 (i) Diseases of the internal organs
Here, in the causes of death mentioned above, some 90-95% of deaths are due to (b) ammonia formation, (c) nitric acid formation, and (d) the formation of poisonous gases by anaerobic bacteria, which are classified under 6 deterioration of water quality, and (a) white spot disease, which is classified under 9 the outbreak of disease.
The above causes (b), (c) and (d) of 6 can be overcome by improving the filtration system and using aerobic bacteria, and the cause (a) of 9 can be overcome satisfactorily by improving the filtration system in the same way, or by treatment with drugs as an alternative method.
Hence, most of the causes of death can be eliminated by improving the filtration system.
That is to say, in order to prevent the ammonia formation of (b) and the nitric acid formation of (c) of 6, an environment in which aerobic bacteria can grow must be established, since aerobic bacteria can convert these materials to harmless materials.
Furthermore, in order to prevent the formation of poisonous gases by anaerobic bacteria of (d), it is necessary to establish an environment such that aerobic bacteria which like oxygen can grow, since anaerobic bacteria dislike oxygen.
Moreover, the white spot disease (a) of 9 is caused by a unicellular ciliate parasite, and this disease tends to propagate explosively on the sea bottom. Therefore, in order to avoid this, it is important to establish an environment in which the flow of water is circulated from the top to the bottom and filtered such that no unicellular ciliates are introduced into the region in which the fish are living.
Thus, in conclusion, in order to establish an environment which is suitable for the keeping of sea-water fish, it is necessary not only to use a tank equipped with an excellent filtering apparatus, but also to use a filtering material which facilitates the propagation of aerobic bacteria. For this reason, development of these filtering materials is very important.
In view of this, sand, active carbon, zeolites and ceramics and the like which are materials in which the growth of aerobic bacteria is facilitated, have been developed and used as filtering materials.
Among these materials, sand is mainly used as the filtering material in many cases, since it is cheap in terms of price (for example, see Japanese Laid-open Patent No. 63-151323).
However, when sand is used, the ammonia and nitric acid in the water are not assimilated satisfactorily. This is considered to result from the fact that the growth of aerobic bacteria is insufficient when sand is used.